Propellant charge for shells having high initial velocity

ABSTRACT

The present invention relates to a propellant charge for shells having high initial velocity, and it is provided primarily, but not exclusively, for sub-caliber or &#39;&#39;&#39;&#39;sabot&#39;&#39;&#39;&#39; shells which while already having a high initial velocity should be improved in this respect even further or, while maintaining this velocity, are to be fired by guns having a relatively reduced barrel length.

ilriied States Paierri 1 1 1 11 3,853,057

Rickert et a1. 4 1 Dec. 10, 11974 [54] PROPELLANT CHARGE FOR SHELLS 2,037,308 4/1936 Brandt 102/492 HAVING HIGH INITIAL VELOCITY 2,600,678 6/1952 ONeill, Jr. 102/101 2,671,401 3/1954 Abramson..,., 102/492 [76] Inventors: Walter Rickert, Lindemannstrasse 3,120,737 11 19 4 Holloway 102 101 59, Dusseldorf; Siegfried Justus, An 3,476,048 11/1969 Barr 102/93 der Juck 76, 507 Berg, Gladbach, 3,509,821 5/1970 Colgate 102/493 both of Germany 3,610,095 10/1971 BlllCk CI 111 102/93 3,742,859 7/1973 Finnegan et a1. .1 102/101 [22] Filed: June 13, 1973 1 21 App]. 3 9,442 Primary ExaminerBenjamin A. Borchelt Assistant Examiner-H. ,1. Tudor Attorney, Agent, or Firm-Parmelee, Miller, Welsh & [30] Foreign Application Priority Data Kratz June 15, 1972 Germany 2229192 52 US. Cl. ..102/49.2, 102/101 [57] ABSTRACT 51 1111. c1. F42b 15/10 The Present mvemlon relates to a propellant Charge [58] Field of Search 102/491, 492 493, 494, for shells having high initial velocity, and it is provided 102/495, 49.6, 49.7, 49.8, 93, 99, 100, 101, Primarily, but not exclusively, for Sub-caliber or 102, 103, 104 hot shells which while already having a high initial velocity should be improved in this respect even fur- [5 6] References Cited ther or, while maintaining this velocity, are to be tired UNITED STATES PATENTS by guns having a relatively reduced barrel length. 1,920,075 7/1933 l-laenichen 102/103 x 13'Claims, 3 Drawing Figures 3 O 3 2 3 4 077/74/fi/ 77Z PROPELLANT CHARGE FOR SHELLS HAVING HIGH INITIAL VELOCITY BACKGROUND OF THE INVENTION It is known that according to the principle of coaccelerated charges, a first primary propulsion charge accelerates the shell together with a second, greater portion of the propellant charge. In result, with relatively low speeds, a high energy may be stored. Upon burning-up of the co-accelerated charge, the effective shell mass will decrease, the gas pressure will drop more slowly, and the shell will have a greater net initial velocity with relatively small barrel lengths since, under other conditions, the pressure drop within the barrel due to acceleration of the propulsion gases may be subject to a direction reversal.

It is an object of the present invention to provide a propellant charge which comprises three components and which permits a greater propellant charge density, a precisely controlled burning characteristic, and the use of the principle of charge accelerated with the shell in barrel weapons without overloading the charge material and the shell material, respectively. Although, the three features as mentioned form, in combination, the object of the invention it is to be recognized that the means to achieve the last mentioned one will require the broadest explanation hereunder.

BRIEF DESCRIPTION OF THE INVENTION According to the invention, the propellant charge comprises at least three components. The first and the second component each are in the form of a multiplicity of disks, those of the first component being substantially thicker than those of the second component. Both types of disks are alternately arranged to form a pile or column. The disks of the first component consist of an explosive which has, under a pressure of about 4,000

DESCRIPTION OF THE DRAWINGS The drawings show a preferred embodiment of the invention. 'The embodiment as illustrated is a subcalib'er shell comprising a double sabot and a splitted propellant charge, the major portion of the latter being accelerated with the shell.

FIG. 1 is a schematic section through a shell and with propellant charge in the design according to the invention;

FIG. 2 is a detail of FIG. 1 which illustrates precisely I the form of the charge; and

' FIG. 3 is a partial section along the line 3-3 of FIG. 1, shown in the same increased scale as used for FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT The shell comprises a shaft including two sabots l2 and 14, a shell tip 16-, and stabilizing vanes 18. The space between sabot l2 and the stabilizing vanes 18 is occupied by the propellant charge portion 20 which is accelerated together with the shell itself, the shaft 10 of the latter carrying further a shaped body 22 made of aluminum, titanium, glass fiber reinforced plastic or the like and having a star-shaped section as shown in FIG. 3. Said shaped body 22 ends in sabot 12. The rear portion of the shaft 10 is hollow and houses a portion 24 of the primary propellant charge. The stabilizing vanes 18 of the shell are embedded in a further portion 26 of the primary propellant charge.

A supplementary charge 28 may be mounted between the two sabots l2 and 14. The igniting means are not shown in the drawings for sake of simplicity and as it is readily within the knowledge of one skilled in the art that igniting conductors may extend through the stabilizing vanes to member 24 if the shell, as assumed for the embodiment as shown, is to be used as cartridge-less ammunition.

FIG. 2 shows the propellant charge in accordance with the invention. For the purpose of illustration only, the thickness of the individual disks is exaggerated while the preferred thickness should be designed as will be discussed later. The propellant charge comprises disks -30 consisting of a first explosive composition, disks 32 consisting of a second explosive composition and having a thickness substantially smaller than that of the first disks 30, and a coating 34 consisting of a third explosive composition and covering the outer surface of the charge column.

It will be noted that the layer thickness of the coating 34 at first increases from rear to tip and decreases again shortly before the sabot for reasons which will be explained later.

DETAILED DESCRIPTION OF SHELL AND PROPELLANT CHARGE Due to the preferred design as explained above, the disks 32 of the second component will be ignited in sequence one after the other in accordance with the continuous burning of the outer coating 34 and the disks of the second component in turn will ignite the disks of the first component 32 which are substantially thicker, this latter ignition occuring almost instantaneously across the entire face of the disks. The thickness of the first component disks will preferably be dimensioned such that it equals substantially one-half of the product of burning propagation velocity, multiplied by the shell acceleration 'period within the gun barrel. If the explosive of the first component has a burning propagation velocity of, say, 30 centimeter per second, the disks of this component will have a thickness of some tenths of a millimeter.

In order to adapt the charge to the gun and to the shell, the thickness of the third component layer 34 may be varied such according to the desired time-locus-characteristic; the thickness of the coating may therefore non-linearly depend upon the axial position of the column. If the coating thickness is very small, there is, however, the danger of detonation in the barrel due to improper manufacture. For this reason it is preferred to use for the first and/or for the third component also, explosives having a so-called mesacharacteristic, i.e., an explosive having a linear burning propagation velocity which decreases with increasing gas pressure, beginning at a known pressure value.

It will be appreciated that when the charge as described is used in combination with a shell with which the charge is accelerated, the third component coating thickness will substantially increase in direction to the shell tip 16 and means must be provided in order to assure this co-acceleration. For this purpose, the propellant charge will take the shape of a hollow cylinder and will be press-fitted to the rear end of the subcaliber portion of the shell or of its sabot. During the acceleration, considerable shearing forces may occur in the charge. Since on the other hand, the shear resistance of the explosives will not exceed a maximum of about 1 kilopond per square millimeter, the contact interface between explosives and said sub-caliber portion may be increased by properly selecting the shape of the latter so that, for example, a star-shaped section 22 will result (FIG. 3). With such a design, the shearing stresses will remain below the mentioned limit up to a velocity of about 500 meters per second provided the initial acceleration will not be chosen too high. In order to permit therebeyond use of the maximum acceleration, the invention provides that in direction to the sabot l2 and shortly before it the third component layer thickness 34 will decrease again. The barrel clearance of the propellant charge may, at first, be selected such that the barrel wall friction which counteracts to the shearing stresses is just counterbalancing because a pressure drop occurs between the bottom of the coaccelerated charge and the sabot. However, since the counterpressure in the charge space must decrease in accordance with the decreasing shell mass in order to achieve a long term maximum acceleration while, on the other hand, the friction forces per barrel length unit increase due to increasing velocity in spite of the increasing barrel wall clearance of the charge, the affect of the friction may be reduced by liberation of combustion gases at the sabot in quantities greater than just cause by purely radial burning of the third component, as provided by the feature mentioned above. When dimensioning the charge in accordance therewith, it must be taken in consideration, of course, that the gas pressure within the charge space will decrease more slowly than in shells not having a co-accelerated propellant charge.

In order to provide a deceleration in the burning of the third component'which may be necessary, the explosives thereof may additionally be phlegmatized. Said phlegmatizing may be effected, in a convenient manne'r, by covering the third component layer, at least on part of its axial length, by a further layer of a fourth composition having a linear burning propogation velocity less than that of the third composition under a pressure of about 1000 atmospheres. One possibility of reducing the load to which a sub-caliber shell is subjected under the conditions of the desired greater acceleration is the provision of a supplementary charge 28 in the space between the sabot l2 and a second sabot 14 mounted closer to the shell tip 16 than the first sabot.

The ignition of this supplementary charge will generate a pre-stress in the shell counteracting at least partly the acceleration forces.

If, as described, the propellant charge is press-fitted onto the shell portion or sabot portion which extends through the entire co-accelerated propellant charge, said shell portion may be made hollow and may house the ignitor charge and, as the case may be, that portion of the propellant charge which provides the initial acceleration. Thereby a stepping of the rear end wall thickness will result which may further reduce the load upon the shell as was the case for the supplementary charge.

Rearwardly of the co-accelerated charge, stabilizing vanes 18 may be positioned while the charge may surround a shaft-like portion 10 of the shell. The shape of the vanes must be compatible with that of the charge. The shaft 10 which will be subjected to extreme mechanical loads may be made at least partly of plasticimpregnated glass fiber material, this material being in some respects superior to steel. In order to isolate it against the charge, it may be provided with a metal coating protection film.

That portion of the propellant charge which is not coaccelerated may have the same design as that of the coaccelerated part, in which case, there will be no necessity to reduce the mechanical stress.

What we claim is:

l. A propellant charge for shells having high initial velocity, said charge comprising a first component, a second component, and a third component, said first component and said second component each comprising a multiplicity of disks alternatinglyarranged to form a column, said disks of said first component having an axial thickness substantially exceeding that of said disks of said second component, said first component being made of an explosive composition, which, under a pressure of about 4,000 atmospheres has a linear burning propagation velocity of less than about 10 meters per second while said second component is made of an explosive composition which, under the same pressure, has a burning propagation velocity of between about and 1,000 meters per second, said third component being a layer covering the surface of said column and consisting of an explosive composition having substantially the properties of the composition of said first component.

2. The propellant charge of claim 1 wherein, the thickness of the first component disks is about one-half of the burning propagation velocity of its explosive composition multiplied by the time period during which the shell is accelerated within a gun barrel.

3. The propellant charge of claim 1 wherein, the radial'thickness of said third component layer varies in axial direction of the shell in accordance with a predetermined burning-time-characteristic.

4. The propellant charge of claim 1 comprising, a shell having stabilizing vanes and at least one sabot and wherein said column is of a hollow-cylindrical configuration and is press-fitted on the rear portion of the shell.

5. The propellant charge in claim 4 wherein, the third component layer has its maximum radial thickness shortly before the sabot, said thickness decreasing forwardly and rearwardly therefrom.

6. The propellant charge of claim 4 comprising, a shell having a first and second sabot wherein a supplementary explosive charge is provided between said two sabots to generate a prestress in the shell during the acceleration within a gun barrel.

7. The propellant charge of claim 4 wherein, the rear shell portion extending into the charge is designed to house a non-accelerated propellant charge portion and to provide a wall thickness stepping.

8. The propellant charge of claim 4 wherein, the charge is disposed between the sabot and stabilizing having a linear burning propagation velocity less than that of the thirdcomposition under a pressure of about 1,000 atmospheres.

12. The propellant charge of claim 1 wherein, the composition of said first component has a linear burning propagation velocity which above a given gas pressure is constant.

13. The propellant charge of claim 1 wherein the composition of said first component has a linear burning propogation velocity which decreases above a given gas pressure. 

1. A propellant charge for shells having high initial velocity, said charge comprising a first component, a second component, and a third component, said first component and said second component each comprising a multiplicity of disks alternatingly arranged to form a column, said disks of said first component having an axial thickness substantially exceeding that of said disks of said second component, said first component being made of an explosive composition, which, under a pressure of about 4,000 atmospheres has a linear burning propagation velocity of less than about 10 meters per second while said second component is made of an explosive composition which, under the same pressure, has a burning propagation velocity of between about 100 and 1,000 meters per second, said third component being a layer covering the surface of said column and consisting of an explosive composition having substantially the properties of the composition of said first component.
 2. The propellant charge of claim 1 wherein, the thickness of the first component disks is about one-half of the burning propagation velocity of its explosive composition multiplied by the time period during which the shell is accelerated within a gun barrel.
 3. The propellant charge of claim 1 wherein, the radial thickness of said third component layer varies in axial direction of the shell in accordance with a predetermined burning-time-characteristic.
 4. The propellant charge of claim 1 comprising, a shell having stabilizing vanes and at least one sabot and wherein said column is of a hollow-cylindrical configuration and is press-fitted on the rear portion of the shell.
 5. The propellant charge in claim 4 wherein, the third component layer has its maximum radial thickness shortly before the sabot, said thickness decreasing forwardly and rearwardly therefrom.
 6. The propellant charge of claim 4 comprising, a shell having a first and second sabot wherein a supplementary explosive charge is provided between said two sabots to generate a prestress in the shell during the acceleration within a gun barrel.
 7. The propellant charge of claim 4 wherein, the rear shell portion extending into the charge is designed to house a non-accelerated propellant charge portion and to provide a wall thickness stepping.
 8. The propellant charge of claim 4 wherein, the charge is disposed between the sabot and stabilizing vanes of the shell, the shell portion between the sabot and said vanes consisting at least in part of glass fiber reinforced plastic.
 9. The propellant charge of claim 8 wherein the glass fiber reinforced plastic stabilizing vanes are metal coated.
 10. The propellant charge of claim 1 which consists of a first portion which is accelerated with the shell and a second portion which is not.
 11. The propellant charge of claim 1 wherein, said third component layer at least on part of its axial length is covered by a further layer of a fourth composition having a linear burning propagation velocity less than that of the third composition under a pressure of about 1,000 atmospheres.
 12. The propellant charge of claim 1 wherein, the composition of said first component has a linear burning propagation velocity which above a given gas pressure is constant.
 13. The propellant charge of claim 1 wherein the composition of said first component has a linear burning propogation velocity which decreases above a given gas pressure. 